Traditionally, email messages are displayed as sequential lists. The email messages can be sorted by one of a variety of criteria, such as date received, subject, sender, size, importance, or flag status. To read an email message, one often has to use his mouse to quickly click on the message twice (i.e., a double-click) in the list to open a message read screen. One can also use a preview screen, which displays the contents of the email message after the user clicks on the message once. With certain devices such as smartphones and tablets, the user can open an email message by pressing on the message with the user's finger.